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| United States Patent |
6,117,926
|
|
Engber
, et al.
|
September 12, 2000
|
Acid-reacted polymer-modified asphalt compositions and preparation
thereof
Abstract
An acid-reacted polymer-modified asphalt composition including (i) 80
weight percent asphalt, (ii) 0.2 to 15 weight percent polymer containing
available epoxy groups, and (iii) an acid effective for promoting chemical
bonding between the asphalt and the polymer, wherein the composition
exhibits substantially improved Dynamic Shear Rheometer stiffness values,
without an appreciable loss in the G" viscous component of the complex
modulus, low temperature creep stiffness and "m" values of the
composition.
| Inventors:
|
Engber; Steven L. (Onalaska, WI);
Reinke; Gerald H. (La Crosse, WI)
|
| Assignee:
|
Mathy Construction Company (Onalaska, WI)
|
| Appl. No.:
|
862333 |
| Filed:
|
May 23, 1997 |
| Current U.S. Class: |
524/59; 524/62; 524/69; 525/54.5 |
| Intern'l Class: |
C08L 095/00; C08L 063/00 |
| Field of Search: |
524/62,69,59
525/54.5
|
References Cited
U.S. Patent Documents
| 2956034 | Oct., 1960 | Simpson | 260/18.
|
| 3202621 | Aug., 1965 | Street | 260/18.
|
| 3876439 | Apr., 1975 | Schneider | 106/287.
|
| 3915730 | Oct., 1975 | Lehureau | 106/279.
|
| 4070532 | Jan., 1978 | Hammer | 526/11.
|
| 4157428 | Jun., 1979 | Hammer | 521/134.
|
| 4238241 | Dec., 1980 | Schneider | 106/281.
|
| 4331481 | May., 1982 | Scheider | 106/283.
|
| 4368228 | Jan., 1983 | Gorgati | 428/110.
|
| 4882373 | Nov., 1989 | Moran | 524/68.
|
| 5070123 | Dec., 1991 | Moran | 524/69.
|
| 5095055 | Mar., 1992 | Moran | 524/59.
|
| 5288392 | Feb., 1994 | Santos | 208/13.
|
| 5306750 | Apr., 1994 | Goodrich | 524/59.
|
| 5331028 | Jul., 1994 | Goodrich | 524/68.
|
| 5367003 | Nov., 1994 | Petcavich | 525/231.
|
| 5576363 | Nov., 1996 | Gallagher et al. | 524/62.
|
| 6011095 | Jan., 2000 | Planche et al. | 524/68.
|
| 6020404 | Jan., 2000 | Planche et al. | 524/59.
|
| Foreign Patent Documents |
| 2 255 173 | Nov., 1972 | DE.
| |
Other References
Lee et al., "Handbook of Epoxy Resins", McGraw Hill Book Co., pp. 1-2 (1982
Reissue).
Lee et al., "Handbook of Epoxy Resins", McGraw-Hill Book Co., New York, pp.
10-11 (1982 Reissue).
Handbook of Epoxy Resins, Henry Lee and Kris Neville, Chapter 15, pp. 15-1
through 15-28; Chapter 22, pp. 22-1 through 22-71; and Chapter 23, pp.
23-1 through 23-25 (Reissue 1982).
|
Primary Examiner: Wilson; Donald R.
Attorney, Agent or Firm: Faegre & Benson LLP
Parent Case Text
This application is a continuation of U.S. patent application Ser. No.
08/402,705, filed Mar. 13, 1995, now abandoned.
Claims
What is claimed is:
1. A composition comprising:
(A) at least about 80 weight percent, based upon the composition, of an
asphalt;
(B) about 0.2 to about 15 weight percent, based upon the composition, of a
vinyl copolymer comprising ethylene and incorporating 0.1 to 15 weight
percent, based on the copolymer, of an ethylenically unsaturated monomer
of 4-21 carbon atoms containing an epoxy group in a manner effective to
provide the vinyl copolymer with available epoxy groups; and
(C) an amount of an acid effective for promoting chemical bonding between
the asphalt and the available epoxy groups of the copolymer and producing
a composition exhibiting substantially improved Dynamic Shear Rheometer
stiffness values, which, when tested with a dynamic shear rheometer at
temperatures ranging from 42.degree. to 82.degree. C., exhibits G*/sin
(.delta.) stiffness values, which are at least about 2 times greater than
stiffness values for the asphalt without polymer or acid, at least about
1.5 times greater than an asphalt/polymer composition without acid, when
tested according to AASHTO TP5, exhibits G" viscous component of complex
modulus values about the same as the asphalt/polymer composition without
acid, when tested according to AASHTO TP5 at temperatures ranging from
4.degree. C. to 40.degree. C., and exhibits low temperature creep
stiffness and "m" values about the same as those exhibited by the asphalt
without polymer or acid, when tested at low temperatures ranging from
-42.degree. C. to 0.degree. C. according to the SHRI Bending Beam Creep
Stiffness test, AASHTO TP 1,
and wherein the acid is selected from a mineral acid, an electron pair
acceptor acid, and a low molecular weight organic acid.
2. A composition comprising:
(A) at least about 80 weight percent, based upon the composition, of an
asphalt;
(B) about 0.2 to about 15 weight percent, based upon the composition, of a
polymer component selected from:
(1) a copolymer containing available epoxy side groups; and
(2) a curable blend comprising 1-99 weight percent of said copolymer, based
upon the blend, and 99-1 percent by weight based upon the blend, of an
organic thermosetting resin with which said copolymer is only functionally
compatible, based upon the blend; and
(C) about 0.02 to about 5.0 weight percent, based upon the composition, of
an acid effective for promoting chemical bonding between the asphalt and
the available epoxy groups of the copolymer such that the asphalt
composition when tested with a dynamic shear rheometer at temperatures
ranging from 42.degree. to 82.degree. C., exhibits G*/sin (.delta.)
stiffness values which are at least about 2 times greater than stiffness
values of the asphalt without polymer or acid, at least about 1.5 times
greater than an asphalt/polymer composition without acid when tested
according to AASHTO TP5, exhibits G" viscous component of complex modulus
values about the same as the asphalt/polymer composition without acid when
tested according to AASHTO TP5 at temperatures ranging from 4.degree. C.
to 40.degree. C., and exhibits low temperature creep stiffness and "m"
values about the same as those exhibited by the asphalt without polymer or
acid when tested at low temperatures ranging from -42.degree. C. to
0.degree. C. according to the SHRP Bending Beam Creep Stiffness test,
AASHTO TP 1; and
wherein said copolymer is obtained from monomers including
(a) 40-90 weight percent of ethylene, based upon the copolymer;
(b) 0-20 weight percent of carbon monoxide, based upon the copolymer;
(c) 5-40 weight percent, based upon the copolymer, of a monomer
copolymerizable therewith, said monomer taken from the class consisting of
unsaturated mono- and dicarboxylic acids of 3-20 carbon atoms, esters of
said unsaturated mono- or dicarboxylic acids, vinyl esters of saturated
carboxylic acids where the acid group has 1-18 carbon atoms, vinyl alkyl
ethers where the alkyl group has 1-18 carbon atoms, acrylonitrile,
methacrylonitrile, alpha-olefins of 3-20 carbon atoms, norbornene and
vinyl aromatic compounds; and
(d) 0.1-15 weight percent, based upon the copolymer, of an ethylenically
unsaturated monomer of 4-21 carbon atoms containing an epoxy group; and
wherein said resin is selected from the group consisting of phenolic
resins, epoxy resins and melamine formaldehyde resins
such that the asphalt composition when tested with a dynamic shear
rheometer at temperatures ranging from 42.degree. to 82.degree. C.,
exhibits G*/sin (.delta.) stiffness values which are at least about 2
times greater than stiffness values of the asphalt without polymer or
acid, at least about 1.5 times greater than an asphalt/polymer composition
without acid when tested according to AASHTO TP5, exhibits G" viscous
component of complex modulus values about the same as the asphalt/polymer
composition without acid when tested according to AASHTO TP5 at
temperatures ranging from 4.degree. C. to 40.degree. C., and exhibits low
temperature creep stiffness and "m" values about the same as those
exhibited by the asphalt without polymer or acid when tested at low
temperatures ranging from -42.degree. C. to 0.degree. C. according to the
SHRP Bending Beam Creep Stiffness test, AASHTO TP1, and wherein the acid
is selected from a mineral acid, an electron pair acceptor acid, and a low
molecular weight organic acid.
3. A composition according to claim 1, wherein the acid is a proton donor.
4. A composition according to claim 1, wherein the acid is selected from
sulfuric acid, phosphoric acid, hydrochloric acid, glacial acetic acid and
nitric acid.
5. A composition according to claim 1, wherein the acid is sulfuric acid in
an amount of about 0.02 to 3.0 weight percent, based on the composition.
6. A composition according to claim 1, wherein the acid is phosphoric acid
in an amount of about 0.05 to 5.0 weight percent, based on the
composition.
7. A composition according to claim 3, wherein the composition further
comprises about 0.5 to about 20 weight percent of a processing oil
selected from the group consisting of a naphthenic oil, a paraffinic oil,
and an aromatic oil.
8. A composition according to claim 3, wherein the copolymer has a melt
index of 1.2 g/sec at 190.degree. C. and is comprised of approximately 57
mole % ethylene, 28 mole % n-butyl acrylate, and 5 mole % glycidyl
methacrylate.
9. A composition comprising:
(A) at least about 60 weight percent, based upon the composition, of an
asphalt,
(B) about 0.2 to about 15 weight percent, based upon the composition, of a
polymer component selected from:
(1) a copolymer containing epoxy side groups; and
(2) a curable blend comprising 1-99 weight percent of said copolymer, based
upon the blend, and 99-1 percent by weight of an organic thermosetting
resin with which said copolymer is only functionally compatible, based
upon the blend;
(C) about 0.02 to about 5.0 weight percent, based upon the composition, of
an acid effective for promoting chemical bonding of the asphalt with the
available epoxy groups of the copolymer such that said composition when
tested with a dynamic shear rheometer at temperatures ranging from
42.degree. to 82.degree. C., exhibits G*/sin (.delta.) stiffness values
which are at least about 2 times greater than the asphalt without polymer
or acid, at least about 1.5 times greater than the asphalt/polymer
compositions without acid when tested according to AASHTO TP5, exhibits G"
viscous component of complex modulus values about the same as an
asphalt/polymer composition without acid when tested according to AASHTO
TP5 at temperatures ranging from 4.degree. C. to 40.degree. C., and
exhibits low temperature creep stiffness and "m" values about the same as
those exhibited by the asphalt without polymer or acid when tested at low
temperatures ranging from -42.degree. C. to 0.degree. C. according to the
SHRP Bending Beam Creep Stiffness test. AASHTO TP1; and
(D) about 0.5 to about 20 weight percent, based upon the composition, of a
processing oil; and
wherein said copolymer is obtained from monomers including
(a) 40-90 weight percent of ethylene, based upon the copolymer;
(b) 0-20 weight percent of carbon monoxide, based upon the copolymer;
(c) 5-40 weight percent, based upon the copolymer, of a monomer
copolymerizable therewith, said monomer taken from the class consisting of
unsaturated mono- and dicarboxylic acids of 3-20 carbon atoms, esters of
said unsaturated mono- or dicarboxylic acids, vinyl esters of saturated
carboxylic acids where the acid group has 1-18 carbon atoms, vinyl alkyl
ethers where the alkyl group has 1-18 carbon atoms, acrylonitrile,
methacrylonitrile, alpha-olefins of 3-20 carbon atoms, norbornene and
vinyl aromatic compounds; and
(d) 0.1-15 weight percent, based upon the copolymer, of an ethylenically
unsaturated monomer of 4-21 carbon atoms containing an epoxy group; and
wherein said resin is selected from the group consisting of phenolic
resins, epoxy resins and melamine formaldehyde resins
such that said composition when tested with a dynamic shear rheometer at
temperatures ranging from 42.degree. to 82.degree. C., exhibits G*/sin
(.delta.) stiffness values which are at least about 2 times greater than
the asphalt without polymer or acid, at least about 1.5 times greater than
the asphalt/polymer compositions without acid when tested according to
AASHTO TP5, exhibits G" viscous component of complex modulus values about
the same as an asphalt/polymer composition without acid when tested
according to AASHTO TP5 at temperatures ranging from 4.degree. C. to
40.degree. C., and exhibits low temperature creep stiffness and "m" values
about the same as those exhibited by the asphalt without polymer or acid
when tested at low temperatures ranging from -42.degree. C. to 0.degree.
C. according to the SHRP Bending Beam Creep Stiffness test, AASHTO TP 1,
and wherein the acid is selected from a mineral acid, an electron pair
acceptor acid, and a low molecular weight organic acid.
10. In a composition comprising:
(A) an asphalt;
(B) a polymer component selected from:
(1) a copolymer containing epoxy side groups; and
(2) a curable blend comprising 1-99 weight percent, based upon the blend,
of said copolymer and 1-99 percent by weight, based upon the blend, of an
organic thermosetting resin with which said copolymer is only functionally
compatible,
wherein said copolymer is obtained from monomers including
(a) 40-90 weight percent of ethylene, based upon said copolymer;
(b) 0-20 weight percent of carbon monoxide, based upon said copolymer;
(c) 5-40 weight percent, based upon said copolymer, of a monomer
copolymerizable therewith, said monomer taken from the class consisting of
unsaturated mono- and dicarboxylic acids of 3-20 carbon atoms, esters of
said unsaturated mono- or dicarboxylic acids, vinyl esters of saturated
carboxylic acids where the acid group has 1-18 carbon atoms, vinyl alkyl
ethers where the alkyl group has 1-18 carbon atoms, acrylonitrile,
methacrylonitrile, alpha-olefins of 3-20 carbon atoms, norbornene and
vinyl aromatic compounds; and
(d) 0.1-15 weight percent of an ethylenically unsaturated monomer of 4-21
carbon atoms containing an epoxy group; and wherein said resin is selected
from the group consisting of phenolic resins, epoxy resins and melamine
formaldehyde resins;
the improvement comprising further incorporating into the composition from
about 0.02 to about 5.0 weight percent, based upon the composition, of an
acid effective for promoting chemical bonding of the asphalt with the
available epoxy groups of the copolymer, so that said composition, when
tested with a dynamic shear rheometer at temperatures ranging from
42.degree. to 82.degree. C., exhibits G*/sin (.delta.) stiffness values
which are at least about 2 times greater than asphalt without polymer or
acid, at least about 1.5 times greater than an asphalt/polymer
compositions without acid when tested according to AASHTO TP5, exhibits G"
viscous component of complex modulus values about the same as the
asphalt/polymer composition without acid when tested according to AASHTO
TP5 at temperatures ranging from 4.degree. C. to 40.degree. C., and
exhibits low temperature creep stiffness and "m" values about the same as
those exhibited by the asphalt without polymer or acid when tested at low
temperatures ranging from -42.degree. C. to 0.degree. C. according to the
SHRP Bending Beam Creep Stiffness test, AASHTO TP 1,
and wherein the acid is selected from a mineral acid, an electron pair
acceptor acid, and a low molecular weight organic acid.
11. A composition according to claim 10, wherein the acid is a proton
donor.
12. A composition according to claim 10, wherein the acid is selected from
sulfuric acid, phosphoric acid, hydrochloric acid, glacial acetic acid and
nitric acid.
13. A composition according to claim 10, wherein the acid is sulfuric acid
in an amount of about 0.02-3.0 weight percent, based upon the composition.
14. A composition according to claim 10, wherein the acid is phosphoric
acid in an amount of about 0.05-5.0 weight percent, based upon the
composition.
15. A composition according to claim 10, wherein the composition further
comprises about 0.5 to about 20 weight percent, based upon the
composition, of a processing oil and wherein the acid is selected from a
mineral acid, an electron pair acceptor acid, and a low molecular weight
organic acid.
Description
FIELD OF THE INVENTION
This invention relates to acid-reacted polymer-modified asphalt
compositions. More particularly, this invention relates to modified
asphalt compositions comprising an asphalt, an acid, and a polymer
selected from (a) certain specific ethylene-carbon monoxide polymers
containing epoxy functional groups or (b) a curable blend of these
polymers with an organic thermosetting resin. The novel asphalt
compositions of this invention, when tested with a dynamic shear rheometer
at temperatures ranging from 42.degree. to 82.degree. C., exhibits G*/sin
(.delta.) stiffness values which are at least about 2 times greater than
the asphalt without polymer or acid, at least about 1.5 times greater than
the asphalt/polymer compositions without acid both when tested according
to AASHTO TP5, exhibits G" viscous component of complex modulus values
about the same as the asphalt/polymer composition without acid when tested
according to AASHTO TP5 at temperatures ranging from 4.degree. C. to
40.degree. C., and exhibit low temperature creep stiffness and "m" values
about the same as those exhibited by the asphalt without polymer or acid
when tested at low temperatures ranging from -42.degree. C. to 0.degree.
C. according to the SHRP Bending Beam Creep Stiffness test, AASHTO TP1.
BACKGROUND OF THE INVENTION
It has long been known that a wide variety of polymeric additives can be
used to produce asphalt and bitumen containing compositions (generally
referred to as "polymer modified asphalt" compositions - PMA compositions)
having certain enhanced properties. All types of asphalt, both naturally
occurring and synthetically manufactured, are suitable for use in this
invention. According to the present invention, the term "asphalt" is meant
to also be inclusive of materials designated by the term "bitumen" and no
distinction is made herein between the two terms. Naturally occurring
asphalt is inclusive of native rock asphalt, lake asphalt, etc.
Synthetically manufactured asphalt is often a by-product of petroleum
refining operations and includes air-blown asphalt, blended asphalt,
cracked or residual asphalt, petroleum asphalt, propane asphalt,
straight-run asphalt, thermal asphalt, etc.
Asphalt has both viscous properties, which allow it to flow, and elastic
properties, which resist flow. At high temperatures, the viscous
properties dominate and the asphalt tends to flow or deform. At low
temperature, the elastic properties dominate and the asphalt tends to
resist flow. By adding certain polymers, these natural characteristics of
asphalt can be modified. The properties improved by the addition of
polymers are resistance to high temperature thermal deformation ("creep"
or "rutting"), as well as resistance to cracking or deforming under
repeated loadings, and, perhaps, the ability to use reduced amounts of
asphalt in asphaltic aggregate compositions without loss of desired
properties.
Goodrich, U.S. Pat. No. 5,331,028, issued Jul. 19, 1994, and assigned to
Chevron, relates to a PMA composition comprising asphalt, a
glycidyl-containing ethylene copolymer and a styrene/conjugated diene
block copolymer. The Goodrich PMA composition can be used in preparation
of asphalt concrete and is said to have enhanced resistance to thermal and
pressure induced deformation.
Another Goodrich patent, U.S. Pat. No. 5,306,750, issued Apr. 26, 1994, and
assigned jointly to Chevron and Du Pont, relates to a thermoplastic
polymer-linked-asphalt product said to evidence enhanced performance
properties even at low polymer concentrations. Among the polymers which
can be used in the PMA compositions of both Goodrich patents are reactant
polymers containing an epoxide moiety which is said to react with the
asphalt. Preferred polymers for both Goodrich compositions are of the
generalized formula:
E--X--Y
E symbolizes an ethylene copolymer unit. X symbolizes a polymer unit of the
formula:
--CH.sub.2 --C(R.sub.1)(R.sub.2)--
wherein R.sub.1 is hydrogen, methyl or ethyl, and R.sub.2 is
--C(O)OR.sub.3, --OC(O)R.sub.3, or --OR.sub.3, and wherein R.sub.3 is a
lower alkyl group. Y symbolizes a copolymer unit of the formula:
--CH.sub.2 --C(R.sub.4)(R.sub.5)--
wherein R.sub.4 is hydrogen or methyl, and R.sub.5 is an epoxide-containing
moiety of the formula
##STR1##
The polymers used in the PMA compositions of these two Goodrich patents are
said to be well known in the art and are described, for example, in U.S.
Pat. No. 4,070,532, issued Jan. 24, 1978 and in U.S. Pat. No. 4,157,428,
issued Jun. 5, 1979, both by Clarence F. Hammer and both assigned to Du
Pont. The polymers described in the Hammer patents and incorporated into
the PMA compositions of the Goodrich patents include a polymer modifier
known by the trade name, ELVALOY.TM. AM, available from Du Pont.
ELVALOY.TM. AM is characterized by Du Pont as a polymer modifier to extend
asphalt pavement life and to provide improvements in asphalt
compatibility, mix stability, handling characteristics and product
performance. Chevron makes available a PMA composition which contains the
Du Pont ELVALOY.TM. AM, typically at polymer levels of about 1-3% by
weight of the PMA composition.
Other processes for forming asphaltic products have been known to utilize
acid treatment in conjunction with the addition of certain other earlier
known polymers. For example, Benjamin S. Santos, U.S. Pat. No. 5,288,392,
issued Feb. 22, 1994, relates to a process for converting acid sludge from
waste oil refineries into an intermediate for production of asphaltic
mixtures. The acid sludge is described as containing such non-specifically
defined components as resinous and asphaltic materials and undefined
hydrocarbon polymers. However, the unidentifiable polymers contained in
this acid sludge are not related structurally or chemically to the
polymers described by the Goodrich and Hammer patents or to the specific
polymers used according to the present invention.
Three patents have issued to Lyle E. Moran, U.S. Pat. No. 4,882,373, issued
Nov. 21, 1989 (Moran I), U.S. Pat. No. 5,070,123, issued Dec. 3, 1991
(Moran II), and U.S. Pat. No. 5,095,055, issued Mar. 10, 1992 (Moran III),
which all relate to premodification of asphalt with an acid, such as HCl
and H.sub.3 PO.sub.4, and then subsequent addition of a thermoplastic
block copolymer.
Specifically, Moran I is said to improve the tensile properties of asphalt
compositions by contacting asphalt with a mineral acid, bubbling an
oxygen-containing gas through the acid treated asphalt, adding a
thermoplastic elastomer to the treated asphalt and finally adding an
unsaturated functional monomer to the polymer modified asphalt. Moran II
and III dispense with the use of oxygen-containing gas and elaborate on a
variety of acids and polymers which may be added to the asphalt
composition to improve its storage stability. The processes of the Moran
II and III patents are said to yield a more highly stabilized PMA
composition by adding the acid simultaneously with or subsequent to the
addition of the polymer.
In addition, Moran III acknowledges an earlier German Offen. 2 255 173 by
Shell, published May 16, 1974, which relates to the addition of styrenic
thermoplastic elastomers and small amounts of phosphoric acid or
hydrochloric acid to asphalt to produce stabilized PMA compositions.
Other patent disclosures contain further descriptions of various acid and
polymer treatments of bituminous or asphaltic materials. According to U.S.
Pat. No. 4,368,228 of Romolo Gorgati, issued Jan. 11, 1983, bitumen
obtained from acid sludge produced by concentrated sulfuric acid treatment
of heavy distillates of asphalt-based petroleum is mixed with certain
thermoplastic polymers to prepare prefabricated waterproofing membrane for
roofing materials. U.S. Pat. No. 3,915,730 of Jean Lehureau, et al.,
issued Oct. 28, 1974, describes a surface paving material which is a
composition of matter comprising 2,2-bis (4-cyclohexanol) propane
diglycidyl ether, and a curing agent with a bituminous material derived
from treatment of petroleum with boiling sulfuric acid.
Processes for acidic treatment of asphaltic or bituminous materials without
the additional presence of polymers are related by two patents to Gordon
Schneider, U.S. Pat. No. 4,238,241, issued Dec. 9, 1980 and U.S. Pat. No.
4,331,481, issued May 25, 1982. According to the Schneider patents, the
amount of asphalt required in asphalt compositions or in asphalt and
aggregate compositions is said to be decreased by the addition of sulfonic
acid to the hot composition mix, without any detrimental effects on the
strength and durability of the final paving material.
Each of these patents describe certain ways of improving the properties of
a variety of asphaltic and bituminous materials. However, there is still a
need for PMA compositions which are able to achieve high stiffness values
at high ambient temperatures while at the same time maintaining needed low
temperature stiffness properties.
According to the present invention, it has unexpectedly and surprisingly
been discovered that the use of certain acids in the formulation of PMA
compositions using certain polymers as described by the Goodrich and
Hammer patents (and particularly ELVALOY.TM.) provides advantageous
benefits to the process of formulating the PMA composition and also lends
desirable properties to the resultant PMA composition. The PMA
compositions of the present invention can be used for long wearing paving
and other applications in climatic zones having a wide range of high
summer and low winter temperatures without unacceptable thermally induced
creep and/or crack problems.
Currently, standardized specifications and test methods for asphaltic
binders are in a state of transition. The asphalt industry, Federal
Highway Administration (FHWA), and individual state transportation
departments are converting to specifications and test methods developed
over several years by the Asphalt Research Output and Implementation
Program of the Strategic Highway Research Program (SHRP). The SHRP
specifications and test methods have been recommended by the FHWA to be in
general, although voluntary, usage for materials for all state and federal
highway programs by 1997. The PMA compositions of the present invention
have all been tested and their properties and use characteristics have
been determined according to the most recent SHRP specifications and test
methods, in addition to many standard PMA tests. The specific tests
methods are described in detail in publication "SHRP-A-370" titled "Binder
Characterization and Evaluation Volume 4: Test Methods" This volume is
published by the Strategic Highway Research Program of the National
Research Council headquartered in Washington, D.C. The specific test
methods used to identify the improved properties of this invention are:
AASHTO TP5 Determining the Rheological Properties of Asphalt Binder Using
a Dynamic Shear Rheometer (DSR), and AASHTO TP1 Determining the Flexural
Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR).
AASHTO is the American Association of State Highway and Transportation
Officials.
SHRP asphalt binder specifications are based primarily on properties
related to performance of the laid down pavement, particularly in regard
to performance under varying pavement conditions of imposed weight load
and temperature. SHRP asphalt binder specifications are designed around
the climatic conditions in the region where the asphalt composition will
be used. SHRP test methods measure properties that are, based on SHRP
supported research, believed to be directly correlated to pavement
performance.
The testing used for the SHRP specifications measures the temperature range
over which a given asphalt exhibits the properties qualifying it as an
acceptable pavement binder for a given set of temperature and traffic
conditions. These specifications utilize measurements of the complex shear
modulus (G*), which represents total applied stress (.tau..sub.total) and
total strain (.epsilon..sub.total), along with the phase angle (.delta.),
which characterizes the viscoelastic nature of the binder. Expected
pavement performance is then represented by a combination of G* with
delta: G*/sin (.delta.), also known as 1/J", for minimum high temperature
stiffness (to resist permanent deformation) and G*.times.sin (.delta.),
also known as G", for maximum intermediate temperature stiffness (to
reduce fatigue cracking). Various SHRP performance grades (PG) have been
established according to the criteria of the testing.
Specific criteria for SHRP performance grades and the tests used in
determining them are described below. FIGS. 1 and 2 provide SHRP
specifications for performance grades PG 52-10 through PG 82-40. The two
numbers that designate the SHRP grade bracket the temperature range, the
SHRP DELTA (SHRP .DELTA.), over which a given SHRP asphalt grade exhibits
the performance properties that have been established by SHRP. If one
simply adds together the absolute values of the two temperatures that
identify the high and low temperatures where all SHRP criteria are met,
the SHRP .DELTA. is calculated. For an asphalt that conforms to a SHRP
grade PG 64-22, one would add 64+.vertline.-22.vertline.and arrive at a
value of 86 degrees. One can, however, take this process one step further.
Applying statistical analysis to the data generated from the SHRP asphalt
binder tests, one can calculate the exact temperatures at which an asphalt
binder will conform to the high and low temperature SHRP requirements. In
essence one can determine a precise SHRP grade for any given asphalt
binder and in so doing be able to calculate a precise SHRP .DELTA. for
that asphalt binder. For example, the asphalt binder above which conforms
to a SHRP grade PG 64-22 could have a SHRP .DELTA. that equals 91.degree.
C. if the high temperature specification were met at exactly 67.degree. C.
and the low temperature specification were met at exactly -24.degree. C. A
precise SHRP grade for this material would be PG 67-24 and the SHRP
.DELTA. would be 91 degrees. Generally speaking to achieve a SHRP .DELTA.
of 98 degrees or greater will require some type of asphalt modification,
and only high quality conventional asphalt binders will exhibit a SHRP
.DELTA. between 92 degrees and 98 degrees.
Dynamic Shear, AASHTO TP5, is determined both before and after simulated
aging in the Rolling Thin Film Oven (RTFO) test to determine a minimum
binder stiffness as exhibited in freshly paved roads up to one year in age
and after the Pressure Aging Vessel (PAV) test to determine the maximum
binder stiffness as exhibited in a pavement up to 5 or more years of age.
Bending Beam Creep Stiffness, AASHTO TP1, is determined after RTFO and PAV
aging. The Bending Beam Creep Stiffness test measures low temperature
stiffness characteristics. A 5".times.1/4".times.1/2" beam of binder
material is molded, cooled to testing temperature, and subjected to an
imposed weight load. Load versus deflection data is collected for 240
seconds. The low temperature specification values are based on the
stiffness value determined at 60 seconds and the absolute value of the
slope (m-value) of the time vs. log (stiffness) curve determined at 60
seconds.
Direct Tension, AASHTO TP3, is also determined after RTFO and PAV aging.
The Direct Tension test measures per cent strain at low temperatures. A
"dogbone" shaped specimen is elongated at low temperature, at a constant
strain rate, until it fractures. The test is generally not performed
unless the Bending Beam Creep Stiffness test passes the slope requirement
and fails the stiffness requirement.
SUMMARY OF THE INVENTION
The present invention provides an acid-reacted polymer-modified asphalt
composition comprised as follows:
(A) at least about 80 weight percent, based upon the composition, of an
asphalt;
(B) about 0.2 to about 15 weight percent, based upon the composition, of a
polymer containing available epoxy groups and having an average molecular
weight of at least 2000; and
(C) an amount of an acid effective for promoting chemical bonding between
the asphalt and the polymer and producing a composition exhibiting
substantially improved Dynamic Shear Rheometer stiffness values, which
when tested with a dynamic shear rheometer at temperatures ranging from
42.degree. to 82.degree. C., exhibits G*/sin (.delta.) stiffness values
which are at least about 2 times greater than stiffness values for the
asphalt without polymer or acid, at least about 1.5 times greater than an
asphalt/polymer composition without acid, when tested according to AASHTO
TP5, exhibits G" viscous component of complex modulus values about the
same as the asphalt/polymer composition without acid, when tested
according to AASHTO TP5 at temperatures ranging from 4.degree. C. to
40.degree. C., and exhibits low temperature creep stiffness and "m" values
about the same as those exhibited by the asphalt without polymer or acid,
when tested at low temperatures ranging from -42.degree. C. to 0.degree.
C. according to the SHRP Bending Beam Creep Stiffness test, AASHTO TP1.
The asphalt composition described immediately above can be used in an
asphalt emulsion comprising 50 to 80 weight percent, based upon the
asphalt emulsion, of the asphalt composition, 0.05 to 5.0 weight percent,
based upon the asphalt emulsion, of a suitable asphalt emulsifying
surfactant, and water.
The present invention also provides a specific acid-reacted
polymer-modified asphalt composition comprised as follows:
(A) about 99.8 to about 80 weight percent, based upon the composition, of
an asphalt;
(B) about 0.2 to about 15 weight percent, based upon the composition, of a
polymer selected from:
(1) an ethylene-carbon monoxide terpolymer containing epoxy side groups;
and
(2) a curable blend comprising 1-99 weight percent of said terpolymer,
based upon the blend, and 99-1 percent by weight of an organic
thermosetting resin with which said terpolymer is only functionally
compatible, based upon the blend; and
(C) about 0.02 to about 5.0 weight percent, based upon the composition, of
an acid effective for promoting chemical bonding between the asphalt and
the polymer; wherein said terpolymer comprises
(a) 40-90 weight percent of ethylene, based upon the terpolymer;
(b) 0-20 weight percent of carbon monoxide, based upon the terpolymer;
(c) 5-40 weight percent, based upon the terpolymer, of a monomer
copolymerizable therewith, said monomer taken from the class consisting of
unsaturated mono- and dicarboxylic acids of 3-20 carbon atoms, esters of
said unsaturated mono- or dicarboxylic acids, vinyl esters of saturated
carboxylic acids where the acid group has 1-18 carbon atoms, vinyl alkyl
ethers where the alkyl group has 1-18 carbon atoms, acrylonitrile,
methacrylonitrile, alpha-olefins of 3-20 carbon atoms, norbornene and
vinyl aromatic compounds; and
(d) 0.1-15 weight percent, based upon the terpolymer, of an ethylenically
unsaturated monomer of 4-21 carbon atoms containing an epoxy group; and
wherein said resin is selected from the group consisting of phenolic
resins, epoxy resins, and melamine formaldehyde resins; such that the
asphalt composition when tested with a dynamic shear rheometer at
temperatures ranging from 42.degree. to 82.degree. C., exhibits stiffness
values [G*/sin (.delta.) at a testing frequency of 10 radians/second],
which are at least about 2 times greater than stiffness values of the
asphalt without polymer or acid, at least about 1.5 times greater than an
asphalt/polymer composition without acid when tested according to AASHTO
TP5, exhibits viscous component of complex modulus [G*.times.sin(.delta.)
or G" at a frequency of 10 radians/sec] values about the same as the
asphalt/polymer composition without acid when tested according to AASHTO
TP5 at temperatures ranging from 4.degree. C. to 40.degree. C., and
exhibits low temperature creep stiffness and "m" values about the same as
those exhibited by the asphalt without polymer or acid when tested at low
temperatures ranging from -42.degree. C. to 0.degree. C. according to the
SHRP Bending Beam Creep Stiffness test, AASHTO TP1.
The specific asphalt composition just described can be used in an asphalt
emulsion comprising 50 to 80 weight percent, based upon the asphalt
emulsion, of the specific asphalt composition, 0.05 to 5.0 weight percent,
based upon the asphalt emulsion, of a suitable asphalt emulsifying
surfactant, and water. This specific asphalt composition can be used in an
asphalt emulsion comprising 30 to 80 weight percent, based on the asphalt
emulsion, of the specific asphalt composition, 0.5 to 20 weight percent,
based on the asphalt emulsion, of a petroleum solvent having a flash
point, as determined by ASTM D 56 or D 92, whichever is appropriate to the
solvent, of 15.degree. C. to 250.degree. C., 0.05 to 5.0 weight percent,
based on the asphalt emulsion, of suitable asphalt emulsifying surfactant,
and water. This specific asphalt composition can be used in an asphalt
emulsion comprising 48 to 80 weight percent, based upon the asphalt
emulsion, of the specific asphalt composition, 0.05 to 5.0 weight percent,
based upon the asphalt emulsion, of a suitable asphalt emulsifying
surfactant, 0.02 to 2.0 weight percent of a cationic adhesion promoter,
and water. This specific asphalt composition can be used in an asphalt
emulsion comprising 28 to 80 weight percent, based on the asphalt
emulsion, of the specific asphalt composition, 0.5 to 20 weight percent,
based on the asphalt emulsion, of a petroleum solvent having a flash
point, as determined by ASTM D 56 or D 92, whichever is appropriate to the
solvent, of 15.degree. C. to 250.degree. C., 0.05 to 5.0 weight percent,
based on the asphalt emulsion, of suitable asphalt emulsifying surfactant,
0.02 to 2.0 weight percent, based on the asphalt emulsion, of a cationic
adhesion promoter, and water.
The specific asphalt composition just described can be used in a cutback
asphalt comprising 40 to 98 volume percent, based on the cutback asphalt,
of the specific asphalt composition, and 2 to 60 volume percent, based on
the cutback asphalt, of a petroleum solvent having a flash point as
determined by ASTM D 56 or D 92, whichever is appropriate to the solvent,
of between 15.degree. C. and 250.degree. C. The specific asphalt
composition just described can be used in a cutback asphalt comprising 38
to 98 volume percent, based on the cutback asphalt, of the specific
asphalt composition, 0.02 to 2.0 weight percent, based on the cutback
asphalt, of a cationic adhesion promoter, and 2 to 60 volume percent,
based on the cutback asphalt, of a petroleum solvent having a flash point
as determined by ASTM D 56 or D 92, whichever is appropriate to the
solvent, of between 15.degree. C. and 250.degree. C.
The present invention also provides an aggregate mix composition comprising
from about 90 to about 99 weight percent, based upon the final mix, of an
aggregate with from about 1 to about 10 weight percent, based upon the
final mix composition, of any of the acid-reacted polymer-modified asphalt
compositions as just previously described.
In addition, the present invention provides a process for preparing an
acid-reacted polymer-modified asphalt composition comprising:
(i) forming a reaction mixture comprising
(A) at least about 80 weight percent, based upon the composition, of an
asphalt;
(B) about 0.2 to about 15 weight percent, based upon the composition, of a
polymer containing available epoxy groups and having an average molecular
weight of at least 2000; and
(C) an amount of an acid effective for promoting chemical bonding between
the asphalt and the polymer; and
(ii) mixing said reaction mixture under conditions sufficient for promoting
chemical bonding between the asphalt and the polymer and producing said
composition, so that said composition when tested with a dynamic shear
rheometer at temperatures ranging from 42.degree. to 82.degree. C.,
exhibits stiffness values [G*/sin (.delta.) at a testing frequency of 10
radians/second], which are at least about 2 times greater than the asphalt
without polymer or acid, at least about 1.5 times greater than the
asphalt/polymer compositions without acid when tested according to AASHTO
TP5, exhibits viscous component of complex modulus (G*.times.sin(.delta.)
or G" at a frequency of 10 radians/sec) values about the same as the
asphalt/polymer composition without acid when tested according to AASHTO
TP5 at temperatures ranging from 4.degree. C. to 40.degree. C., and
exhibits low temperature creep stiffness and "m" values about the same as
those exhibited by the asphalt without polymer or acid when tested at low
temperatures ranging from -42.degree. C. to 0.degree. C. according to the
SHRP Bending Beam Creep Stiffness test, AASHTO TP1.
The present invention also provides a process for preparing an acid-reacted
polymer-modified asphalt composition comprising:
(i) forming a reaction mixture comprising
(A) about 99.8 to about 80 weight percent, based upon the composition, of
an asphalt;
(B) about 0.2 to 15 weight percent, based upon the composition, of a
polymer selected from
(1) an ethylene-carbon monoxide terpolymer containing epoxy side groups;
and
(2) a curable blend comprising 1-99 weight percent, based upon the blend,
of said terpolymer and 1-99 percent by weight, based upon the blend, of an
organic thermosetting resin with which said terpolymer is only
functionally compatible; and
(C) about 0.02 to about 5.0 weight percent, based upon the composition, of
an acid effective for promoting chemical bonding of the asphalt and the
polymer; and wherein said terpolymer comprises
(a) 40-90 weight percent of ethylene, based upon the terpolymer;
(b) 0-20 weight percent of carbon monoxide, based upon the terpolymer;
(c) 5-40 weight percent, based upon the terpolymer, of a monomer
copolymerizable therewith, said monomer taken from the class consisting of
unsaturated mono- and dicarboxylic acids of 3-20 carbon atoms, esters of
said unsaturated mono- or dicarboxylic acids, vinyl esters of saturated
carboxylic acids where the acid group has 1-18 carbon atoms, vinyl alkyl
ethers where the alkyl group has 1-18 carbon atoms, acrylonitrile,
methacrylonitrile, alpha-olefins of 3-20 carbon atoms, norbornene and
vinyl aromatic compounds; and
(d) 0.1-15 weight percent, based upon the terpolymer, of an ethylenically
unsaturated monomer of 4-21 carbon atoms containing an epoxy group; and
wherein said resin is selected from the group consisting of phenolic
resins, epoxy resins, and melamine formaldehyde resins; and
(ii) mixing said reaction mixture under conditions sufficient for promoting
chemical bonding between the asphalt and the polymer and producing said
composition, so that said composition when tested with a dynamic shear
rheometer at temperatures ranging from 42.degree. to 82.degree. C.,
exhibits stiffness values [G*/sin (.delta.) at a testing frequency of 10
radians/second], which are at least about 2 times greater than the asphalt
without polymer or acid, at least about 1.5 times greater than an
asphalt/polymer composition without acid when tested according to AASHTO
TP5, exhibits viscous component of complex modulus [G*.times.sin(.delta.)
or G" at a frequency of 10 radians/sec] values about the same as the
asphalt/polymer composition without acid when tested according to AASHTO
TP5 at temperatures ranging from 4.degree. C. to 40.degree. C., and
exhibits low temperature creep stiffness and "m" values about the same as
those exhibited by the asphalt without polymer or acid when tested at low
temperatures ranging from -42.degree. C. to 0.degree. C. according to the
SHRP Bending Beam Creep Stiffness test, AASHTO TP1.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 provide SHRP specifications for asphalt binders grades PG 52
through PG 82.
FIG. 3 is a three dimensional graph of effects for response `1/J"=1`.
FIG. 4 is a three dimensional graph of effects for response `1/J"=2.2`.
FIG. 5 is a three dimensional graph of effects for response `G"=5000`, the
complex shear modulus.
FIG. 6 is a three dimensional graph of effects for response `LTCS @ 300`,
the low temperature creep stiffness in kilopascals.
FIG. 7 is a three dimensional graph of effects for response `m @ 0.300`,
the stress relaxation at low temperatures.
DETAILED DESCRIPTION OF THE INVENTION
Many presently available asphalt compositions are not able to meet the
demanding requirements of the newer SHRP specifications for climate zones
having widely varying climatic conditions of low winter and high summer
temperatures. Polymer modification according to the present invention
provides improved PMA compositions to meet the newer SHRP specifications
and thus of a wider variety of climate zones.
As has been discussed above, the present invention involves the use of acid
of sufficient concentration and acidity to initiate the reaction of
certain polymers with asphalt in preparing PMA compositions such that the
composition, when tested with a dynamic shear rheometer at temperatures
ranging from 42.degree. to 82.degree. C., exhibits G*/sin (.delta.)
stiffness values, which are at least about 2 times greater than the
asphalt without polymer or acid, at least about 1.5 times greater than the
asphalt/polymer compositions without acid when tested according to AASHTO
TP5, exhibits G" viscous component of complex modulus values about the
same as the asphalt/polymer composition without acid when tested according
to AASHTO TP5 at temperatures ranging from 4.degree. C. to 40.degree. C.,
and exhibits low temperature creep stiffness and "m" values about the same
as those exhibited by the asphalt without polymer or acid when tested at
low temperatures ranging from -42.degree. C. to 0.degree. C. according to
the SHRP Bending Beam Creep Stiffness test, AASHTO TP1.
When referred to throughout this specification and the claims, G*/sin
(.delta.) stiffness values are as calculated at a testing frequency of 10
radians/second when tested according to AASHTO TP5. When referred to
throughout this specification and the claims, G" viscous component of
complex modulus values mean G*.times.sin(.delta.) or G" values as
calculated at a frequency of 10 radians/sec when tested according to
AASHTO TP5 at temperatures ranging from 4.degree. C. to 40.degree. C.
All types of asphalt, both naturally occurring and synthetically
manufactured, are suitable for use in this invention. According to the
present invention, the term "asphalt" is meant to also be inclusive of
materials designated by the term "bitumen" and no distinction is made
herein between the two terms. Naturally occurring asphalt is inclusive of
native rock asphalt, lake asphalt, etc. Synthetically manufactured asphalt
is often a by-product of petroleum refining operations and includes
air-blown asphalt, blended asphalt, cracked or residual asphalt, petroleum
asphalt, propane asphalt, straight-run asphalt, thermal asphalt, solvent
extracted asphalt or asphalt pitches, etc. A preferred asphalt for the
present invention has an initial viscosity at 60.degree. C. of 20 to
50,000 poise. "Initial viscosity", as herein intended, designates the
asphalt viscosity prior to addition of polymers and/or acids. Preferably,
the asphalt has a viscosity of 50 to 10,000, even more preferably 50 to
4000, and most preferably 50 to 3000 poise.
The acids which may be used in the present invention include those acids
which are an electron pair acceptor (also sometimes referred to as a Lewis
acid) or a proton donor (also sometimes referred to as a Bronsted acid).
Electron pair acceptor acids suitable for use according to this invention
are inclusive of boron trifluoride and its complexes, aluminum
trichloride, stannic tetrachloride, aluminum sulfate, aluminum chloride
and ferric chloride, or any blends thereof. Proton donor acids suitable
for use according to this invention are inclusive of mineral acids, such
as sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid, and
low molecular weight organic acids, such as glacial acetic acid or any
blends thereof.
In addition, it has also been discovered that anionic soaps, that is alkali
salts of long chain fatty acids or rosin acids, may also functionally
replace an acid according to the present invention. Such soaps include
saponified tall or other crude commodity oils or manufactured oils such as
dodecylbenzene sulfonic acid or refined or reacted oils such as refined
tall oils, rosin acids, oleic acid, stearic acid, or sulfonated versions
of any of the above.
It has further been found that styrene butadiene rubber latexes, generally
referred to as SBR latexes, will, when added to an asphalt with subsequent
removal of the water present in the SBR latex and followed by addition of
ELVALOY.TM. as described above, result in the improvement noted with the
addition of anionic soaps. This is believed to occur because of the use of
potassium soaps containing disproportionated rosin acids as the dispersion
system for the emulsion polymerization process used to manufacture the SBR
latex. This improved result has been found to occur whether or not true
anionic SBR latex is used or so called cationic SBR latex is used. In
point of fact "cationic" SBR latexes are formed as anionic latexes to
which a cationic surfactant is post added. The basic chemistry of the
emulsion polymerization of both products is the same.
The specific amount of acid to be added will vary according to the specific
acid used, the specific asphalt, the specific polymer and the desired
characteristics of the final PMA composition, but can readily be
determined by the skilled worker. Generally, the acid should be of
sufficient concentration and acidity to effect complete reaction of the
asphalt with the polymer. The presently preferred acids are sulfuric acid
or phosphoric acid and typical amounts of acid range between about 0.05 to
5.0% by weight of the final PMA blend, with an amount of about 0.10% to
0.75% by weight of the final PMA blend presently preferred.
The polymers which can be used according to the present invention are known
and are commercially available. Suitable polymers contain available epoxy
groups and have an average molecular weight of at least 2000. The term
"available epoxy groups", for the purposes of this invention, means epoxy
groups which are chemically and physically situated within the polymer
molecule so that they are accessible for chemical bonding with the
asphalt.
Suitable polymers for use in this invention are described, for example, in
U.S. Pat. No. 4,070,532, issued Jan. 24, 1978 and in U.S. Pat. No.
4,157,428, issued Jun. 5, 1979, both to Clarence F. Hammer and both
assigned to Du Pont. Such polymers are selected from:
(1) an ethylene-carbon monoxide terpolymer containing epoxy side groups;
and
(2) a curable blend comprising 1-99 weight percent of said terpolymer,
based upon the blend, and 99-1 percent by weight of an organic
thermosetting resin with which said terpolymer is only functionally
compatible, based upon the blend; and wherein said terpolymer comprises
(a) 40-90 weight percent of ethylene, based upon the terpolymer;
(b) 0-20 weight percent of carbon monoxide, based upon the terpolymer;
(c) 5-40 weight percent, based upon the terpolymer, of a monomer
copolymerizable therewith, said monomer taken from the class consisting of
unsaturated mono- and dicarboxylic acids of 3-20 carbon atoms, esters of
said unsaturated mono- or dicarboxylic acids, vinyl esters of saturated
carboxylic acids where the acid group has 1-18 carbon atoms, vinyl alkyl
ethers where the alkyl group has 1-18 carbon atoms, acrylonitrile,
methacrylonitrile, alpha-olefins of 3-20 carbon atoms, norbornene and
vinyl aromatic compounds; and
(d) 0.1-15 weight percent, based upon the terpolymer, of an ethylenically
unsaturated monomer of 4-21 carbon atoms containing an epoxy group; and
wherein said resin is selected from the group consisting of phenolic
resins, epoxy resins, and melamine formaldehyde resins.
A particularly suitable polymer modifier for use according to the present
invention is ELVALOY.TM. AM available from Du Pont. ELVALOY.TM. AM is
characterized by Du Pont as a polymer modifier to extend asphalt pavement
life and to provide improvements in asphalt compatibility, mix stability,
handling characteristics and product performance. In addition, other
polymers of the "ELVALOY.TM. FAMILY," that is, co-polymers containing
glycidyl methacrylate or glycidyl acrylate as epoxy-bearing moieties, may
also be used.
The specific amount of polymer to be added to the asphalt will vary
according to the specific polymer used, the specific asphalt, the specific
acid and the desired characteristics of the final PMA composition, but can
readily be determined by the skilled worker. Typical amounts of polymer
range between about 1-8% by weight of the final PMA blend.
Various processing oils may also be added to the PMA compositions of this
invention. Such oils are marketed by the Shell Oil Company, Sun Refining,
and other petroleum refiners and include oils classified as naphthenic,
paraffinic, or aromatic oils. Preferred oils exhibit low pour points, low
volatility, and efficacy in a manner where the least added amount reduces
the temperature at which the stiffness of the binder exceeds
3.times.10.sup.5 kilopascals and the "m" value of the binder falls below
0.300 when tested according to the SHRP Bending Beam Flexural Creep
Stiffness test, AASHTO TP1.
The acid-reacted PMA compositions of the present invention can be used in
an aggregate mix composition comprising from about 90 to about 99 weight
percent, based upon the final mix, of an aggregate with from about 1 to
about 10 weight percent, based upon the final mix composition, of an
acid-reacted PMA compositions. For the purposes of this invention, the
term aggregate refers any typical aggregate, including a mixture of sand
and gravel, any natural or synthetic aggregate, recycled asphalt material
(RAP), and granulated re-used or recycled pavement material.
The term "functional compatibility" in the practice of the present
invention refers to a degree of compatibility between two polymer
materials that might appear to be incompatible as evidenced by two phases.
Nevertheless, the blend is strong and tough because the two materials are
functionally compatible. This functional compatibility occurs because the
two phases are interdependent and not pure phases of the starting resins.
Each phase contains a small amount of the other resin. In fact, in molten
two-phase blends of this type, there is an equilibrium condition with a
constant mirgration of molecules across the phase boundaries. One theory
suggests that the cooled sample has some molecules trapped part way across
the boundary and thereby imparting the improved mechanical performance.
Functional compatibility between two resin materials is also discussed in
U.S. Pat. No. 4,157,428 (Hammar).
Because the acid-reacted polymer-modified asphalt compositions of this
invention are hydrophobic and have good adhesiveness and weatherability,
they can also be used for such purposes as a coating for roofing shingles.
Among advantages to be noted in the process of formulating the PMA
compositions of this invention are completion of reaction in distinctly
shorter processing times and at distinctly lower processing temperatures.
Processing is complete in no more than about 24 hours and at temperatures
ranging from about 135.degree. C. to about 185.degree. C., preferably
about 150-170.degree. C. Shorter processing times and lower processing
temperatures mean economic savings in terms of having the final product
PMA compositions more quickly available and in terms of freeing processing
equipment for further re-use.
SPECIFIC EXAMPLES
Example A
A comparative prior art formulation, PMA Formulation 1, not containing an
acid was made by combining
Amoco AC-5: an asphalt available from Amoco; and
ELVALOY.TM. AM: 1.75% by weight of the final blend.
In the following manner: asphalt, under low shear agitation, was heated to
a temperature of about 155.degree. C. wherein the polymer was introduced.
The temperature was then increased to and maintained at 165.degree. C.,
the "reaction temperature." Within approximately one hour, the polymer was
successfully dispersed and an initial G*.times.sin (.delta.) reading was
taken. The sample was maintained at the reaction temperature, with
agitation, for a total of 66 hours whereupon the full battery of SHRP
tests were conducted. During the 66 hours reaction time, a total of eight
G*.times.sin(.delta.) measurements were taken to monitor the progress of
the reaction.
A comparative prior art formulation, PMA Formulation 2, not containing an
acid was made by combining
Amoco AC-5: an asphalt available from Amoco; and
ELVALOY.TM. AM: 1.75% by weight of the final blend.
In the following manner: asphalt, under low shear agitation, was heated to
a temperature of about 155.degree. C. wherein the polymer was introduced.
The temperature was then increased to and maintained at 185.degree. C.,
the "reaction temperature." Within approximately one hour, the polymer was
successfully dispersed and an initial G*.times.sin (.delta.) reading was
taken. The sample was maintained at the reaction temperature, with
agitation, for a total of 48 hours. The full battery of SHRP tests were
not run on Formulation 2 because of the similarity of the viscous modulus
profiles between Formulation 1 and 2. During the 48 hours reaction time, a
total of eleven G*.times.sin (.delta.) measurements were taken to monitor
the progress of the reaction.
To illustrate the improvement over prior art, PMA Formulation 3, according
to this invention, was made by combining
Amoco AC-5: an asphalt available from Amoco;
ELVALOY.TM. AM: 1.75% by weight of the final blend; and
Sulfuric acid: 0.5% by weight of the final blend.
In the following manner: asphalt, under low shear agitation, was heated to
a temperature of around 155.degree. C. wherein the polymer was introduced
Once the polymer was dispersed, an aliquot of the sample was removed, and
reduced in temperature to 140.degree. C. prior to the introduction of the
sulfuric acid. Once the visible reaction, some slight foaming, had ceased,
an initial sample was taken. After 24 hours at 140.degree. C., the acid
reacted aliquot was subjected to the full battery of SHRP tests.
A comparison of PMA FORMULATIONS 1, 2 and 3 indicates that the effect of
the addition of the acid in FORMULATION 3, according to this invention, is
threefold: first is the time in which the formulation reaches its final
properties; second is the relative impact of temperature on the
G*.times.sin(.delta.) stiffness values (TABLE 1) between Formulation 1
(165.degree. C.), Formulation 2 (185.degree. C) and Formulation 3
(140.degree. C.); and third is that the final SHRP properties (TABLE 2)
represent an improvement over those where acid is not used:
TABLE 1
______________________________________
60.degree. C. G* .times. SIN(.delta.) at
Trial 66 or 48
SAMPLE HOUR 24 HOUR HOUR
______________________________________
AMOCO AC-5 0.53 kpa -- --
FORMULATION 1 0.70 kPa 1.16 kPa 1.44 kPa @ 66
FORMULATION 2 0.76 kPa 1.15 kpa 1.50 kpa @ 48
FORMULATION 3 2.46 kPa 2.39 kpa --
______________________________________
TABLE 2
__________________________________________________________________________
TEMPERATURES [DEG C.] AT TARGET SHRP PROPERTIES
1/J" @
UNAGED RTFO PAV
58.degree. C.
.degree. C. @ 1/J" =
@ 1/J" =
@ G" =
@ STIFF. =
@ SLOPE =
SHRP .DELTA.
SAMPLE [kPa] 1 kPa 2.2 kPa 5000 kPa 300 MPa 0.300 [DEG C.]
__________________________________________________________________________
AMOCO AC-5
0.70
55.3 56.3 14.0 -23.4 -22.7 88.00
FORMULATION 1 1.86 64.0 65.3 14.9 -21.6 -22.0 95.60
FORMULATION 3 3.66 71.1 74.1 13.3 -23.4 -23.5 104.50
__________________________________________________________________________
Through the use of time-temperature superposition SHRP researchers
developed techniques for determining the low temperature performance
properties of asphalt at a test temperature 10.degree. C. warmer than the
actual target temperature. This shift in testing temperature greatly
reduces the amount of time needed to conduct a low temperature stiffness
test. To accurately identify the correct low temperature at which a SHRP
graded asphalt will perform, one must subtract 10.degree. C. from the
temperature at which the low temperature stiffness equals 300 MPa or the
temperature at which the "m" (slope) value equals 0.300. Therefore, in the
example above the Amoco AC-5 will have acceptable stiffness at a service
temperature of -33.4.degree. C. and acceptable slope at -32.7.degree. C.
Understanding the procedure is important for determining the correct SHRP
grade of an asphalt and also for calculating the SHRP .DELTA..
The SHRP .DELTA. is a measure of the effective temperature range of a
pavement binder. The correct high temperature grade is determined by
examining the 1/J" values of the unaged and RTFO samples. Whichever sample
achieves the 1/J" SHRP target value at the lowest temperature will
determine the high temperature grade of the asphalt. The correct low
temperature grade is determined by first subtracting 10.degree. C. from
both the stiffness and slope results and then determining which parameter
meets the SHRP target values at the highest temperature. This is the
temperature at which all SHRP low temperature criteria are met. If one
then adds the value of the high temperature grade to the absolute value of
the low temperature grade, the sum is what we are calling the "SHRP
.DELTA.". In the SHRP data listed above the SHRP .DELTA. for Amoco AC-5 is
calculated as 55.3.degree.+.vertline.-32.7.degree..vertline. which is
88.degree. as shown. The SHRP .DELTA. of the Amoco AC-5 improves by
7.6.degree. C. with the addition of 1.75% ELVALOY.TM. AM and another
8.9.degree. C. with the addition of 0.5% H.sub.2 SO.sub.4. The increase in
the SHRP .DELTA. for Formulation 3, the current invention, is largely
attributed to the increase in the unaged 1/J" measurement which is 5.2
times greater than the asphalt without polymer or acid and 2.0 times
greater than the asphalt/polymer composition without acid. Surprisingly,
the acid treated sample showed some improvement in low temperature
properties compared to the sample of Formulation 1.
Example B
According to the blending methods of Example A with the exception that
samples containing ELVALOY.TM. AM without acid were reacted, unagitated,
for only 24 hours at 165.degree. C., the following formulations were
prepared with
Moosejaw 200/300, a pen graded asphalt from Moosejaw Refining
LW 130, a paraffinic process oil produced by Sun Refining Co.
ELVALOY.TM. AM, and concentrated sulfuric acid.
at the following levels:
TABLE 3
______________________________________
SAMPLE 200/300 LW 130 ELVALOY .TM. AM
SULFURIC ACID
______________________________________
24A 90.00% 10.00% -- --
25A 87.85% 9.76% 1.99% 0.45%
27A 99.50% -- -- 0.50%
27B 89.55% 9.95% -- 0.50%
30A 88.00% 10.00% 2.00% --
30B 98.00% -- 2.00% --
______________________________________
Full SHRP testing was conducted on all these compositions in addition to
the base asphalt, Moosejaw 200/300:
TABLE 4
__________________________________________________________________________
SLOPE
TEMPERATURES OF LOG
(DEG C.) AT TARGET SHRP PROPERTIES 1/J" VS
UNAGED RTFO PAV TEMP
TRIAL
@ 1/J" =
@ 1/J" =
@ G" =
@ STIFF. =
@ SLOPE =
LINE [log
SHRP .DELTA.
SAMPLE 1 kPa 2.2 kPa 5000 kPa 300 MPa 0.300 (kPa)/.degree. C.] [DEG.
__________________________________________________________________________
C.]
200/300
54.00
45.3 11.40
-24.70
-25.10
-0.051
88.70
NEAT
24A 41.7 45.3 -0.9 -35.9 -35.1 -0.57 86.80
25A 60.7 76.1 -2.6 -36.6 -36.0 -0.039 106.70
27A 60.8 64.2 10.4 -25.9 -26.6 -0.060 96.70
27B 50.2 54.7 -2.8 -36.2 -34.6 -0.051 94.80
30A 48.4 52.8 -1.6 -36.2 -33.8 -0.040 92.20
30B 60.9 63.3 10.9 -24.9 -26.6 -0.044 95.80
__________________________________________________________________________
The effects of the three asphalt additives and their interactions can be
resolved in the above data; doing so indicates that, in addition to the
effects of the ELVALOY.TM. AM and the sulfuric acid individually, there is
an effect from their interaction. Beginning with the neat 200/300, the
SHRP grade is a PG 52-34 with a precise SHRP .DELTA. of 88.7.degree. C.
Adding 10% LW 130 (Trial 24A) depresses the unaged 1/J" temperature over
12.degree. C. and improves the BBR measurements by 10.degree. C.; the
result is a hypothetical PG 40-40 with a precise SHRP .DELTA. of
86.8.degree. C., nearly 2.degree. C. worse than the original material. By
adding 0.5% H.sub.2 SO.sub.4 to the asphalt/oil blend (Trial 27B), an
increase of 8.0.degree. C. is observed in the SHRP .DELTA.. By adding 2.0%
ELVALOY.TM. AM to the asphalt/oil blend (Trial 30A) and reacting it for 24
hours at 165.degree. C., the SHRP .DELTA. increases 5.4.degree. C. Taken
individually, the acid and ELVALOY.TM. AM add a total of 13.4.degree. C.
to the SHRP .DELTA. of the asphalt/oil blend.
When 1.75% ELVALOY.TM. AM is added to the asphalt/oil blend of Trial 24A
and then treated with 0.5% H.sub.2 SO.sub.4 after the polymer is dispersed
(about 1 hour at 140.degree. C.), the SHRP .DELTA. is increased by
18.degree. C., substantially more than the sum of the individual effects
of the two additives.
This composition, Trial 25A, was blended and reacted at temperatures at or
around 140.degree. C. and had essentially achieved its final properties in
two hours. This compares to 24 hours at 165.degree. C. for Trial 30A. {It
has since been determined that the unaccelerated ELVALOY.TM. Reaction,
that is the prior art reaction without the presence of acid according to
the present invention, may take temperatures up to 190.degree. C. for
periods up to 72 hours, depending on the base asphalt, to proceed to
completion.]
Another measure of the quality of a pavement binder is the slope of the
temperature vs. log (1/J") regression line: The closer the slope of the
temperature versus log (1/J" stiffness) line gets to zero the less
temperature dependent the material being tested becomes. In units of log
(kPa) per degree Centigrade, the slope of the neat 200/300 was -0.051.
This decreased to -0.057 with the addition of oil (24A), improved to
-0.051 with the subsequent addition of H.sub.2 SO.sub.4 (27B) or to -0.040
with the addition of the ELVALOY.TM. AM. With the addition of polymer and
acid, the slope was increased to -0.039.
Most surprising and unexpected in these findings is the observation that
the addition of H.sub.2 SO.sub.4 may have a beneficial effect on the low
temperature BBR test results. It is commonly observed that the addition of
polymers, in general, can have a deleterious effect on these properties,
particularly on the BBR "m" value. The addition of acid in the current
invention, as observed above, may reverse this effect.
Example C
In addition to the polymer ELVALOY.TM. AM, which has a Melt Index of 12
g/10 sec at 190.degree. C. and a monomer composition of 66.75% ethylene,
28% n-butyl acrylate, and 5.25% glycidyl methacrylate (the source of the
pendant epoxide functionality), other ELVALOY.TM. polymers with different
melt indices and different compositions have been evaluated with respect
to the current invention. Two such compounds, "ELVALOY.TM. A" and
"ELVALOY.TM. C" are characterized by Du Pont as follows:
TABLE 5
______________________________________
% n-Butyl % Glycidyl
Melt Index % Ethylene Acrylate Methacrylate
______________________________________
ELVALOY A
3.90 60.30 28.30 11.40
ELVALOY C 4.90 54.50 34.40 11.10
______________________________________
Using a mixed refinery source, penetration graded 200/300 asphalt the
following blends were mixed at 165.degree. C. and reacted for 24 hours:
TABLE 6
______________________________________
% % % %
LW ELVALOY .TM. ELVALOY .TM. ELVALOY .TM. %
Trial 130 A C AM H.sub.2 SO.sub.4
______________________________________
48A 3.00 -- -- 1.75 0.25
51A 3.00 1.75 -- -- 0.26
GHR 3.00 1.75 -- -- --
043
52A 3.00 -- 1.75 -- 0.25
GHR 3.00 -- 1.75 -- --
042
______________________________________
Subjective observation of the above samples indicated that the acid treated
trials may provide more useful binders as evidenced by the lack of "gel.".
"Gel," as commonly encountered in the polymer modification of asphalt, may
result from polymer/polymer crosslinking as opposed to a polymer/asphalt
reaction; at worst, it may develop into an unpumpable, dilatant liquid. An
example of this undesirable condition is illustrated by the 135.degree. C.
Brookfield viscosity (ASTM test method D 4402) values for trials 51A and
GHR 043 as shown in Table 7. The SHRP criteria for this parameter is a
value of 3.00 Pa*sec (Pascal seconds) or less. As can be seen from the
data the sample prepared with 1.75% of ELVALOY.TM. A according to this
invention exhibited an acceptable Brookfield viscosity, while the sample
prepared with 1.75% of ELVALOY.TM. A without the addition of acid
exhibited a Brookfield viscosity more than 5 times greater and exhibited a
gel-like physical appearance.
TABLE 7
__________________________________________________________________________
TEMPERATURES
135.degree. C. (DEG C.) AT TARGET SHRP PROPERTIES
Brookfield
UNAGED
RTFO PAV
TRIAL
Viscosity
@ 1/J"=
@ 1/J" =
@ G" =
@ STIFF.
@ SLOPE =
SHRP .DELTA.
SAMPLE [Pa * s] 1 kPa 2.2 kPa 5000 kPa 300 MPa 0.300 [DEG C.]
__________________________________________________________________________
41A 0.505
63.10
64.80
9.10 -27.10
-26.40
99.50
51A 1.360 75.30 71.70 7.80 -28.60 -26.50 108.20
GHR 043 6.400 61.40 57.50 6.10 -29.00 -28.30 95.80
52A NO TEST 65.90 69.20 6.50 -28.60 -27.70 103.60
GHR 042 NO TEST 58.10 57.80 6.90 -28.80 -28.30 86.10
__________________________________________________________________________
The increases in the Temperatures at which the 1/J"=1 values are achieved
are quite marked in the acid treated samples: 13.9.degree. C. for the
unaged ELVALOY.TM. A compositions (51A vs GHR 043) and 7.8.degree. C. for
the unaged ELVALOY.TM. C samples (52A vs GHR 042), 14.2.degree. C. for the
RTFO ELVALOY.TM. A compositions and 11.4.degree. C. for the RTFO
ELVALOY.TM. C samples. The BBR stiffness values are essentially unaffected
and the slight fall off in the "m" values are easily offset by the large
gains in the SHRP .DELTA..
The combined effects of additional glycidyl methacrylate and increased
molecular weight (generally inversely correlated to Melt Index) with
respect to the current invention are illustrated by comparing Trials 51A
and 52A with Trial 41A. Trial 41A has SHRP .DELTA.'s 8.7.degree. C. and
4.1.degree. C. less than Trials 51A and 52A respectively, even though the
levels of all additives are virtually identical for each trial. A logical
conclusion which can be drawn from this data is that higher epoxy
(glycidyl methacrylate) loadings and increased molecular weight improve
SHRP test properties. While the practical ceiling for molecular weight and
glycidyl methacrylate loadings has not been established, the above
observations and data suggest that the present invention may extend those
ceilings.
Explanation of Response Surface Plots
The plot in FIG. 3 is a three dimensional response surface plot of the data
summarized in Example C. As can be seen from this response surface plot
the temperature at which 1/J" achieves 1 kPa (the SHRP minimum for unaged
asphalt) increases as the per cent of Elvaloy AM increased (the "ELAM %"
axis). Also the 1/J" temperature increases and then tends to level off as
the amount of sulfuric acid increases (the "H2S04% axis). However,
portions of the surface that represent various combinations of these two
materials show a much steeper rate of increase of the 1/J"=1 kPa
temperature. In addition these interior data points correspond to a higher
1/J"=1 kPa temperature than either of the component materials
independently.
The plot in FIG. 4 is a three dimensional response surface plot of the data
summarized in Example C. As can be seen from this response surface plot
the temperature at which 1/J" achieves 2.2 kPa (the SHRP minimum for the
RTFO residue) increases as the per cent of Elvaloy AM increases (the "ELAM
%" axis). Also the 1/J" temperature increases and then tends to level off
as the amount of sulfuric acid increases (the "H2S04% axis). However,
portions of the surface that represent various combinations of these two
materials show a much steeper rate of increase of the 1/J"=2.2 kPa
temperature. In addition these interior data points correspond to a higher
1/J"=2.2 kPa temperature than either of the component materials
independently.
The plot in FIG. 5 is a three dimensional response surface plot of the data
summarized in Example C. As can be seen from this response surface plot
the temperature at which the the G*.times.sin(.delta.), G", value of the
PAV residue achieves 5000 kPa is essentially unchanged by the addition of
Elvaloy and is decreased slightly by the increased level of H.sub.2
SO.sub.4.
The plot in FIG. 6 is a three dimensional response surface plot of the data
summarized in Example C. As can be seen from this response surface plot
the temperature at which the slope, at 60 seconds, of the Temp versus log
Stiffness curve (the m-value) achieves 0.300 (the SHRP minimum for the PAV
residue) decreases as the per cent of Elvaloy AM increases (the "ELAM %"
axis). Also the m-value temperature decreases as a second order function
as the amount of sulfuric acid increases (the "H2S04% axis). Also, it can
be seen that the impact of the sulfuric acid is more pronounced than the
impact of the Elvaloy. Typically, polymer additions have a deleterious
impact or no effect on the m-value; the fact that Elvaloy alone does
beneficially impact the m-value was unsuspected. The additional
enhancement as a result of the acid addition was even more unsuspected and
surprising.
The plot in FIG. 7 is a three dimensional response surface plot of the data
summarized in Example C. As can be seen from this response surface plot
the temperature at which the low temperature creep stiffness (LTCS)
achieves 300 MPa (the SHRP maximum for the PAV residue) decreases as the
per cent of Elvaloy AM increases (the "ELAM %" axis). Also the LTCS
temperature decreases as a second order function as the amount of sulfuric
acid increases (the H2S04% axis). Also, it can be seen that the impact of
the sulfuric acid is more pronounced than the impact of the Elvaloy.
Typically, polymer additions have little or no effect on the LTCS value;
the fact that the Elvaloy alone does beneficially impact the LTCS was
unsuspected. The additional enhancement as a result of the acid addition
was even more unsuspected and surprising.
Example D
Example C illustrated the effect, in ELVALOY.TM. type polymers, of higher
epoxide (glycidyl methacrylate) loadings in conjunction with higher
molecular weights. The present example illustrates that the epoxide group
can be part of the polymer backbone (in contrast to the pendent group
provided by the glycidyl methacrylate) and that improved properties appear
to be closely linked to a sufficient acid/epoxy ratio when molecular
weight is held constant. Using low molecular weight polybutadiene resins
available from Elf Atochem (Trade name: Poly BD Resin R45HT), with 0%, 3%,
and 6% oxirane oxygen (i.e. epoxide oxygen), blends were made with a mixed
refinery source, penetration graded 120/150 asphalt. These blends were
prepared by mixing the following compositions at 165.degree. C. and
reacting them for about 20 hours:
TABLE 8
______________________________________
H.sub.3 PO.sub.4 /
Oxirane
% Resin in % Oxirane Oxygen Ratio
the modified Oxygen % by wt. in the
Trial blend in Resin H.sub.3 PO.sub.4 blend
______________________________________
84A 1.50 3.00 -- --
84B 1.50 3.00 0.50 11.10
84C 1.50 6.00 -- --
84D 1.50 6.00 0.50 5.60
85B 1.50 6.00 0.40 4.40
86A 1.50 -- 0.40 --
86B 1.50 -- -- --
120/150, -- -- -- --
Neat
______________________________________
Dynamic shear rheometer readings were taken on the unaged samples at 1 and
20 hours:
TABLE 9
______________________________________
% Increase, Temperature
1/J" @ 58.degree. C., Acid Treated [Deg C.] @
10 rad/s Over control 1/J" = 1.0 kPa
Trial @ 1 hr @ 20 hr @ 1 hr
@ 20 hr
@ 1 hr
@ 20 hr
______________________________________
84A 0.873 1.078 NA NA NO NO
TEST TEST
84B 1.767 GELLED NO NO
TEST TEST
84C 1.051 1.218 NA NA 58.70 59.80
84D 1.906 2.625 81.40 115.50 NO NO
TEST TEST
85B 1.646 2.293 56.60 88.30 62.20 64.50
86A 1.152 1.355 26.30 33.90 59.40 60.70
86B 0.912 1.012 NA NA 57.40 58.30
120/150, 1.071 NA NA NA 58.70 NA
Neat
______________________________________
The effect of the non-epoxidized polybutadiene, Trial 86B, is essentially
that of a plasticizing oil; that is, the 1/J" value is less than that for
the neat 120/150 asphalt. When phosphoric acid is introduced, as in Trial
86A, there is only a 33.9% improvement in the 1/J" value at 20 hours. When
the acid is introduced to asphalt/resin solutions where the resin contains
epoxy groups, as in Trials 84B, 84D, and 85B, the increases in 1/J" at one
hour, compared to the same solutions without acid (Trials 84A, 84C, and
84C, respectively), improve from 56.6% to 81.4% to 102.0% as the H.sub.3
PO.sub.4 /Oxirane Oxygen Ratio increases from 4.4 to 5.6 to 11.1.
The importance of having sufficient acid, as measured by the H.sub.3
PO.sub.4 /Oxirane Oxygen Ratio, is illustrated by comparing the results of
Trial 84B with Trial 84D. The resin with only 3% oxirane oxygen (Trial
84B) shows a greater initial boost than the resin with 6% oxirane oxygen
(Trial 84D) when the H.sub.3 PO.sub.4 loading was kept at 0.5% by weight
of the final composition. Trials 84D and 85B exhibit a comparison between
identical resin blends but with slightly differing acid additions. Trial
84D contains 0. 1% more H.sub.3 PO4 than does Trial 85B; and more
importantly the H.sub.3 PO.sub.4 /oxirane oxygen ratio of 84D is 27.3%
{(5.6-4.4)/4.4*100%} greater than the same ratio for Trial 85B. When the %
increase in 1/J" of Trial 84D over the no acid control (Trial 84C) is
compared to the % increase in 1/J" of Trial 85B over the no acid control;
one finds that Trial 84D has a 1/J" increase that is 27.2% greater than
the increase for Trial 85B (115.5%-88.3%).
In the ELVALOY.TM.-acid system, less sensitivity to the acid/epoxy ratio is
observed. Perhaps due to the saturated backbone of this family of
polymers, less of the acid is consumed in nonproductive chemistry than
with the unsaturated backbone of the poly butadiene resins.
Example E
In addition to preparing the asphalt blends of the present invention
according to the method of Example B, preparation of other asphalt blends
according to the present invention can be successfully carried out by
pre-adding the acid to the asphalt at temperatures in excess of
approximately 155.degree. C., agitating with low shear mixing until all
foaming ceases, and then adding the required polymer. If an epoxide
bearing polymer, such as ELVALOY.TM. AM, is added, at temperatures lower
than about 155.degree. C., to an asphalt pretreated with acid; the rate at
which the polymer reacts with the acid may exceed the rate at which the
polymer can be melted and dispersed into the asphalt. This will result in
the polymer at the surface of the polymer pellet crosslinking with itself,
becoming insoluble in the asphalt and consequently not permitting the
remaining unreacted polymer in the pellet from dispersing into the
asphalt.
Aside from this processing disadvantage to pretreating the asphalt, there
is virtually no difference in the properties of the final product. To
illustrate this, two identical blends, 76A and 76B, were produced with
73.38% of a domestic crude source AC-20, a viscosity graded asphalt
24.46% of a domestic crude source asphalt flux
1.59% ELVALOY.TM. AM, and
0.57% of a 85.9% (ortho) phosphoric acid
In the following manner:
76A: A 75/25 blend of AC-20/flux was heated to about 160.degree. C., with
steady, low shear agitation, whereupon it was treated, with the required
H.sub.3 PO.sub.4 and reacted until all foaming ceased. The temperature was
then increased to about 170.degree. C. and the ELVALOY.TM. AM was
introduced. Steady low shear agitation was continued until the polymer was
dispersed. The sample was then put in a 170.degree. C. oven to continue
reaction.
76B: A 75/25 blend of AC-20/flux was heated to about 170.degree. C., with
steady, low shear agitation, and the ELVALOY.TM. AM was introduced. After
an hour at this temperature, the polymer was fully dispersed and the
required H.sub.3 PO.sub.4 was introduced and reacted until all foaming
ceased. The sample was then put in a 170.degree. C. oven to continue
reaction. The two runs compare as follows:
TABLE 10
__________________________________________________________________________
SLOPE
TEMPERATURES OF LOG
(DEG C.) AT TARGET SHRP PROPERTIES 1/J" VS
UNAGED RTFO PAV TEMP
TRIAL
@ 1/J" =
@ 1/J" =
@ G" =
@ STIFF. =
@ SLOPE =
LINE [log
SHRP .DELTA.
SAMPLE 1 kPa 2.2 kPa 5000 kPa 300 MPa 0.300 (kPa)/.degree. C.] [DEG.
__________________________________________________________________________
C.]
76A 72.50
71.20
18.20
-18.6 -17.6 -0.039
98.80
76B 72.30 71.50 18.30 -18.1 -17.3 -0.040 98.80
__________________________________________________________________________
There is, as can be seen from the data, virtually no difference between the
trials with pre- or post-addition of the acid with respect to the final
properties.
With respect to operational concerns, there may be advantages with either
procedure. Using the post-addition method, the material can be produced at
lower temperatures without the possibility of reacting the polymer before
it is totally dispersed--this is desirable with respect to reduced energy
costs and reduced stack emissions from the production site. If, however,
it is advantageous, for some reason, to conduct the reaction at an
elevated temperature--at a refinery, for example, with time constraints
and a high temperature asphalt stream--then pre-treatment of the asphalt
with acid may be desirable.
Example F
A direct comparison between the acid initiated and conventional ELVALOY.TM.
blend was conducted using materials similar to those in Example E
a domestic crude source AC-20, a viscosity graded asphalt,
a domestic crude source asphalt flux,
ELVALOY.TM. AM, and
85.9% (ortho) phosphoric acid.
These components were used to blend Trials 74A and 74B in the following
manner:
Trial 74A: A 79/21 blend of AC-20/flux was heated to 180.degree. C. and
1.6% ELVALOY.TM. AM was added with steady, low shear agitation until it
was fully dispersed. The sample was then put into a 180.degree. C. oven,
with no agitation, for continued reaction.
74B: A 79/21 blend of AC-20/flux was heated to 160.degree. C. and 1.6%
ELVALOY.TM. AM was added with steady, low shear agitation until it was
fully dispersed. Maintaining that temperature, 0.58% H.sub.3 PO.sub.4
(85.9%) was then introduced. Agitation was continued until all foaming
ceased whereupon the sample was put into a 160.degree. C. oven, with no
agitation, for continued reaction.
A comparison of the two trials is shown below:
TABLE 11
______________________________________
Trial 64.degree. C. G*/SIN(.delta.)[1/J" in kPa] at 10 rad/s at
Sample 1 HOUR 16 HOUR 40 HOUR
48 HOUR
120 HOUR
______________________________________
74A 0.399 0.862 0.912 0.929 1.107
74B 1.749 1.725 1.765 1.669 1.819
74A/74B 4.40 2.00 1.90 1.80 1.60
______________________________________
The acid initiated reaction (74B), it can be seen, ultimately reaches a
1/J"=approximately 1.6 times that of the conventional blend (74A), as per
the claim of the present invention. By the end of one hour and thereafter,
74B had achieved at least 90% of its final (120 hour) 1/J". 74A did not
achieve this extent of reaction until about 60 hours. Further, an
examination of the log 1/J" vs temperature lines indicates that after each
time increment, the acid initiated sample exhibited less temperature
dependency than the heat initiated one:
TABLE 12
______________________________________
Trial SLOP OF LOG (1/J") VS TEMP LINE AT
Sample 1 HOUR 16 HOUR 40 HOUR
48 HOUR
120 HOUR
______________________________________
74A -0.052 -0.052 -0.049 -0.048 -0.046
74B -0.043 -0.048 -0.045 -0.044 -0.042
______________________________________
By adding the above described polymers to asphalt in the presence of acid,
according to the present invention, sufficient processing oils can be
added to enable attaining the very lowest SHRP performance grades, while
also minimizing the required amounts of polymer, which is generally the
most expensive component.
Example G
To further show the usefulness of the present invention over the
conventional process for producing ELVALOY.TM. modified asphalt and to
also demonstrate the efficacy of using acid blends the following
experimental runs were compared. All blends were produced using a mixed
refinery source blend of asphalts with a penetration of 105 dmm.
TABLE 13
__________________________________________________________________________
Blend
Temp @
Temp @
Temp @
Temp @
% & 1/J" = 1 1/J" = 1 1/J" = 1 1/J" = 1
ELVALOY .TM. Storage kPa at kPa at kPa at kPa at
Trial # AM % H.sub.3 PO.sub.4 % H.sub.2 SO.sub.4 Temp 1 hr 18 hr 24 hr
42 hr
__________________________________________________________________________
91A 2.00 0.00 0.00 190.degree. C.
62.7.degree. C.
65.5.degree. C.
66.degree. C.
66.degree. C.
91B 1.60 0.50 0.00 160.degree. C. 69.5.degree. C. 68.4.degree. C.
69.1.degree. C. 69.3.degree. C.
91C 1.60 0.25 0.15 160.degree.
C. 70.4.degree. C. 70.2.degree.
C. 69.4.degree. C. 68.6.degree.
__________________________________________________________________________
C.
Even though Trial 91A contained 25% more polymer than did Trials 91B and
91C and was maintained at a temperature 30.degree. C. hotter than Trials
91B and 91C, the results show that the blends produced in accordance with
this invention have achieved greater 1/J" stiffness values over similar
time periods. If 1/J" values as high as those obtained in Trials 91B and
91C are not required, the level of polymer addition could be reduced even
more thus adding to the economic benefit of this invention.
The present invention provides several advantages to the formulator who is
using epoxide functionalized polymer additives to improve the properties
of asphalt. In particular the present invention provides advantages to the
formulator who is employing ELVALOY.TM. as the epoxide functionalized
polymer to modify asphalt. We have discovered that through the use of low
levels of acid in conjunction with ELVALOY.TM. that both the time and the
temperature required to complete the reaction of the ELVALOY.TM. with the
asphalt are substantially reduced. Additionally, we have discovered that
the amount of ELVALOY.TM. which must be added to any particular asphalt to
achieve a desired set of finished product characteristics can be reduced
when the finished product is made following this invention. These
improvements to the finished product are all achieved with no loss of
performance properties of the finished asphalt blend as measured using
SHRP test methods or other currently utilized test procedures.
The particular role played by the acid in the formulation of the PMA
compositions according to the present invention is not completely
understood. However, it is not necessary to understand the mechanism of
the interaction of the various components in forming the present novel PMA
compositions of this invention in order to practice this invention.
According to the present invention, other polymers known as desirable
asphalt modifiers may also be added to the asphalt, along with the acid
and the polymers as described above. For example, styrene/conjugated diene
block copolymers derived from styrene and a conjugated-diene, such as
butadiene, may also be added. Such copolymers are available under the
tradenames KRATON.TM., from Shell Chemical Co., EUROPRENE SOL.TM., from
Enichem, and FINAPRENE.TM., from Fina Chemical Co. Procedures for
preparing these copolymers are also available from U.S. Pat. No.
3,281,383, issued Oct. 25, 1966 to R. P. Zelinski, et al., and U.S. Pat.
No. 3,639,521, issued Feb. 1, 1972 to J. L. Hsieh. Additionally, ethylene
copolymerized with esters such as vinyl acetate, methyl acrylate, n-butyl
acrylate, ethyl acrylate or the like may be blended with the polymers
described in this invention to achieve suitable results. It is also
anticipated that polyethylene and the products of this invention may be
blended to produce suitable results. It is also contemplated that other
polymers known in the industry as asphalt modifiers may also be added to
the asphalt compositions according to the present invention.
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